Leather articles are used in various products such as watchbands and handbags. In particular, the look of leather increases commodity values of watchbands and handbags, increasing the level of consumer satisfaction. Also, it is needless to say that such goods are designed to allow leathers to directly touch the skin, enhancing the added value of products.
It is necessary to make a large leather sheet in advance to produce such leather articles. The skin of a desirable animal such as crocodile or cow is obtained for producing a leather. As the obtained skin has poor durability for use, it is subjected to tanning. As a result of tanning, it becomes possible to impart heat resistance and durability, thereby producing a leather from the skin. The thus obtained leather is dyed with a desirable color or subjected to surface shaping so as to make a leather sheet. The leather sheet is cut to a shape for intended use and processed by adhering a core material or the like using an adhesive so as to manufacture leather articles. Manufacturing of leather articles in the above manner has been widely known and traditionally employed.
Tanning is a method for obtaining a durable leather by processing the skin. In the past, tannin obtained from plants was used, but treatment with tannin is inadequate in terms of resistance, flexibility, and elasticity. In view of this, the recent trend is to use a chrome tanning agent (basic chromium sulfate) for chrome tanning that realizes high heat resistance, flexibility, and elasticity. Chrome tanning accounts for more than 90% of tanning in a global scale, indicating that it has the greatest economic importance. A hydrated chrome complex is embedded between carboxyl groups of glutamic acid and aspartic acid in the collagen peptide structure so that a soft durable leather can be obtained. Chrome tanning is widely known in the art and explained on the website of, for example, the Japanese Association of Leather Technology (JALT).
In addition to the above, Patent Document 1 discloses a method of tanning, comprising treating a leather and skin using a tanning agent containing deglycosylated iridoid and/or deglycosylated secoiridoid other than a tanning agent containing genipin.